Temperature control system



July 30, 1940. w. L. MCGRATH 2,209,926

TEMPERATURE CONTROL SYSTEM Filed March 23, 1936 4 Sheets-Sheet l y 1940. w. 'MCGRATH 2,209,926

TEMPERATURE CONTROL SYSTEM Filed March 23, 1936 4 Sheets-Sheet 2 Mai Owl-M6 741 TEMPERATURE CONTROL SYSTEM Filed March 23, 1936 4 Sheets-Sheet 3 19s I Y i Q @483 I8! 7 a 84 f l I86 William L M grafiz July 30,1940; w. M GRATH 2,209,926 I TEMPERATURE CbNTROL SYSTEM I V 2G2 m 21 21c; Qes

TO SLIDERS TO OIL. TO CONTROL 468(47 FOR BURNER I82 MOTOR l7 CONTROLLNG OF FIGS OF FIGS. l8 3 PROPORTIONING Patented July 30, 1940 UNITED STATES PATENT OFFICE TEMPERATURE CONTROL SYSTEM of Delaware Application March 23, 1936, Serial No. 70,366

17 Claims.

This invention relates to temperature control systems. Conventional heating systems using space thermostats of the o and off type for controlling a heater for heating a space supply heat at substantially full capacity to the space upon a call for heat by the space thermostat and supply substantially no heat to the space when the space thermostat is satisfied. In other words large amounts of heat 'are delivered to the space upon a call for heat and substantially no heat is delivered to the space when the space temperature is satisfied. Due to this intermittent supply of large amounts of heat to the space and due to the inherent lag or inertia of such heating systems, overshooting and undershooting of the space temperature is brought about.

It is known that by maintaining the temperature or pressure orrate of fiow of the heating medium at a predeterminedvalue so as to supply just the correct amount of heat to the space to satisfy the heating load on the system, the space temperature may be maintained at a desired value. Stated in another way, for a given heating load .on the system the temperature or pressure or rate of fiow of the heating medium may be adjusted to supply suflicient heat to the space to maintain the temperature of the space constant. It follows then that for every heating load on the system, there must be a corresponding temperature or pressure or rate of flow value of the heating medium to maintain the space temperature constant. Specifically, upon an inpressure or rate of flow of the heating medium must be increased to supply additional heat to make up for the increase in the'heating load. Likewise, for a decrease in the heating load the temperature or pressure or rate of flow of the heating medium must be decreased. Therefore, in order to make a completely automatic control system to adjust the temperature or pressure or rate of flow of the heating medium to maintain the space temperature constant in the manner outlined above, some means responsive to the load on the heating system is required for adjusting the temperature or pressure or rate of flow of the heating medium.

Means in the form of outdoor thermostats have been used to adjust the temperature of the heating fluid to attempt to vary the temperature thereof in accordance with varying heat losses from the space ascaused'by changes in outdoor .temperature. At the best, these systems are only partially accurate in their control since they do crease in the heating load the temperature or not respond to other conditions that vary the heating load such as wind velocity, solar radiation, the heat retaining capacity of the space, opening and closing of doors and windows and,

body heat given oh by persons congregating in 5 the space.

It is, therefore, the prime object of this invention to provide a heating control system responding to changes in the heating load as caused by any or all variablesto maintain the space temperature substantially constant.

It is found that when the heating load on the system is relatively small, there is a demand for heat only a relativelysmall percent of the total time and that when the heating load is great 15 there is a demand for heat a relatively large percent of the total time. For every heating load there is a corresponding percent of time during which there is a demand for heat. Therefore, the period or percent of time during which there is- 20 a demand for heat forms an ideal indication of the heating load on the heating system. It follows, therefore, that adjusting the temperature or pressure or rate of flow of the heating medium in accordance with the percent of time that there is a demand forheat causes adjustment of the temperature or pressure or rate of flow of the heating medium in accordance with the load on the heating system.

It is, therefore, an object of this invention to provide a temperature control system for a heating means whereby the temperature or pressure or rate of flow of the heating medium is adjusted in accordance with the percent of time during which there is a demand for heat to maintain the space temperature at a substantially constant value.

The various manners in which this mode of operation is accomplished and the, novel structure utilized form objects of this invention. 46

For a more thorough understanding of my invention reference is made to the accompanying specification, claims and, drawings, in which drawings:

Figure 1 shows diagrammatically one form of my invention as applied to a space heating system utilizing a space thermostat for accomplishing the control function;

a space thermostat for performing the control function; and

Figure 4 is a diagrammatic illustration of a control system that may be applied to the forms of the invention shown in Figures 1 and 3, whereby control in response to the average temperature of a building is obtained.

Referring now to Figure 1, I have designated a space, the temperature of which is to be controlled, at Ill. The space may be heated by a radiator I I which is connected to a riser I2 which in turn is connected to a header I3 which receives a supply of heating fluid from a supply pipe I5 under the control of a valve l 4. The heating fluid delivered through the pipe I3 and riser I2 to the radiator I I may be either steam or hot water.

The valve I4 is adapted to be operated by a motor I6, which may be of the proportioning type shown and described in application Serial No. 673,236 filed by Louis L. Cunningham on May 27, 1933, now Patent No. 2,160,400, dated May 30, 1939. The motor I6 is controlled by a second motor generally designated at I1, which is in turn controlled by a space thermostat generally designated at I8. If steam is used as the heating fluid andif the supply of steam may not be constant, a pressure controller generally designated at I9 may be used in combination with the motor I1.

The valve 4 is operated by a valve stem 2| which is connected by a pitman 22 to a crank pin 23 operated by the proportioning motor I6. The crank pin is operated through a reduction gear train 24 by motor rotors 25 and 26 upon energization of field windings 21 and 28, the arrangement being such that when the field winding 21 is energized the valve 4 is moved towards an open position and when the field winding 28 is energized the valve I4 is moved towards a closed position. The motor rotors 25 and 26 also operate a bevelled gear 29 which meshes with another bevelled gear 30. The bevelled gear 30 operates fingers 3| and 32, which are preferably made of insulating material, in such manner as to break contact between the contacts of limit switches 33 and 24 upon extreme opening or closing movements of the valve I4. The bevelled gear 30 also operates a slider 35 with respect to a balancing potentiometer coil 36. The arrangement is such that when valve I4 is moved towards an open position the slider 35 is moved to the right with 'respect to the balancing potentiometer coil 36 and when the valve I4 is moved towards a closed position, the slider 35 is moved to'the left with respect to the balancing potentiometer coil 36. When the valve I4 is moved to a closed position the finger 3| opens the limit switch 33 and when the valve I4 is moved to an extreme open position the finger 32 opens the limit switch 34.

The motor generally designated at H comprises rotors 38 and 39 which are operated by the field windings 46 and 4| respectively. The rotors 38 and 39 operate through a reduction gear train generally designated at 42, to rotate an elon-- gated screw 43. Mounted on the screw 43 is a nut 44 which carries a member 45, preferably made of insulating'material. The member 45 in turn carries sliders 46 and-41 which are adapted to slide across a potentiometer coil 48. The nut 44 also carries an abutment member 49, preferably made of insulating materiaL. which is adapted :to engage and open limit switches 50 and 5|. The arrangement is such that when the field winding 40 is energized the screw 43 is rotated in such direction as to move the nut 44 wane leit, and

when the field winding 4| is energized the screw 43 is rotated in the opposite direction to move the nut 44 to the right.

The space thermostat, generally designated at I8, may comprise a bimetallic element 53 for operating contacts 54 and 56 with respect to stationary contacts 55 and 51. The contacts 56 and 51 are spaced farther apart than contacts 54 and 55, so that upon a decrease in space temperature the contact 54 first engages the contact 55 and then the contact 56 engages the contact 51, and upon an increase in space temperature the engagement between the contacts 56 and 51 is broken first and then the engagement between contacts 54 and 55 is broken. For purposes of illustration, it is assumed that the contacts 54 and 55 make and break at substantially '72 degrees and that the contacts 56 and 51 make and break at substantially 70 degrees.

This form of the invention contemplates the use of a relay coil 59 for operating switch arms 60, 6| and 62. coil 59, the switch arms 60, 6| and 62 are moved into engagement with contacts 63, 64 and 65 respectively. Upon deenergization of the relay coil 59 the switch arms 60, 6| and 62 are moved out of engagement with their respective contacts and the switch arms 6| and 62 are moved into engagement with contacts 66 and 61, this last movement of the switch arms 60, 6| and 62 being ac- Upon energization of the relay complished by means of springs, gravity or other means, not shown This invention also contemplates the use of a relay comprising relay coils 69 and 10 for influencing a core 1|. The core 1| is suitably connected to a switch arm 12 which cooperates with spaced contacts 13 and 14. When the relay coil 69 is energized more than the relay coil 10, the switch arm 12 is moved into engagement with the contact 13. When the relay coil 10 is ener-' gized more than the coil 69, the switch arm 12 is moved into engagement with the contact 14,

and when the relay coils 69 and 10 are equally energized, the switch arm 12 is maintained in a position midway between the contacts 13 and 14.

Line wires leading from source of power, not shown, are designated at 16 and 11. A primary 18 of a step-down transformer'19 having a secondary is connected across the line wires 16 and 11. One end of the secondary 80 is connected by a wire 8| to the contact 55 of the space thermostat I8. The contact 51 thereof is connected by wires 82 and 83 to one end of the relay coil- 59 and the other end of the relay coil 59 is connected by a wire 84 to the other end of the secondary 80. The bimetallic element 53 of the space thermostat I8 is connected by a wire 85 to the relay contact 63, and the switch arm 60 oooperating with the contact 631s connected by a wire 86 to the junction of wires 82 and '83.

degrees, the contact 54 is moved into engagement with the contact 55 and upon a further decrease in space temperature to a value illustrated 'at 70 degrees, the contact 56 is moved'into engagement with the contact 51. This engagement of 1 60 When the space temperature decreases to 7,2

the contacts 56 and 51 completes a circuit from 85, contact 63, switch arm 6'), wires 86 and 83,

' relay coil 59 and wire 84, back to the secondary 80. This circuit maintains the relay coil 59 energized until such time as the space temperature shall rise to 72 degrees to break contact between the contacts 54 and 55.

A primary 88 of a step-down transformer 89 having a secondary 90 is also connected across the line wires 16 and 11. One end of the secondary 90 is connected by wires 9| and 92 to the left end of the relay coil 69, and the other end of the secondary 90 is connected by wires 93 and 94 to the right end of the relay coil 10, the other ends of the relay coils 69 and 10 being connected together. Therefore, the relay coils 69 and 10 are connected across the secondary 90. The left hand end of the coil 69 is also connected by a protective resistance 95 and wires 96, 91 and 98 to the right hand end of the potentiometer coil 48 and to the right hand end of the balancing potentiometer coil 36. In a like manner, the right hand end of the relay coil 10 is connected by a protective resistance 99 and wires I00, Il, I02 and I03 to the left hand end of the potentiometer coil 48 and the left hand end of the balancing potentiometer coil 36. Thejunction of the coils 69 and 10 is connected by wires I04 and I05 and a resistance I06 to the switch arm 62 operated by the relay coil 59. The junction of the coils 69 and is also connected by wires I04, I01 and I08, a resistance I09 and a wire IIO, to the slider 35 associated with the balancing potentiometer coil 36. The contact 65 associated with the switch arm 62 is connected by a wire I II to the slider 46 and the contact 61 is connected by a wire 2 to the slider 41. From the above connections itis seen that the secondary 90, the relay coils 69 and 10, the potentiometer coil 48 and the balancing potentiometer coil 36, are all connected in parallel. Likewise, it is seen that the junction of coils 69 and 10, either of the sliders 46 and 41, and the slider 35 associated with the balancing potentiometer coil 36, are connected together.

The contact 13 is connected by wire II4 to a small number of turns of the relay coil 69 and the contact 14 is connected by a wire II5 to a small number of turns of the relay coil 10. The switch arm 12 is connected'by a wire II6 to the junction of the field windings 21 and 28 of the proportioning motor I6. The field winding 21 is connected by a wire II1 to the limit switch 34, which in turn is connected by wires II8 and 93 to one end of the secondary 90. Likewise, 'the' field winding 28 -is connected by a wire II9 through the limit switch 33 and wires I20 and 9I to the other end of the secondary 90.

Upon a call for heat by the space thermostat I8 so as to energize the relay coil 59 to move the switch arm 62 into engagement with the contact 65, a circuit is completed from the junction of the relay coils 69 and 10 through wires I04 and I05, resistance I06, switch arm 62, contact 65, wire I I I, slider 46, the left hand end of the potentiometer coil 48, wires I02, IOI and I00, and protective resistance 99, to the relay coil 10. Due to the parallel relationship pointed out above, completion of this circuit causes partial short-circ'uiting of the relay coil 10 by reason of the fact that the resistance in the potentiometer coil 48 is less at the left hand end thereof than at the right hand end thereof when the'slider 46 is placed in communication with the junction of. the relay coils 69 and 10 by movement of theswitch arm 62 into engagement with contact 65. This partial short-circuiting of the relay coil 10 decreases the energlzation thereof and increases the energization of the relay coil 69 to move the switch arm 12 into engagement with the contact 13. This causes completion of a circuit from the secondary 90 through wires 9I and 92, a small number of turns of the relay coil 69, wire II4, contact 13, switch arm 12, wire I I6, field winding 21, wire II1, limit switch 34, and wires II8 and 93, back to the secondary 90. Completion of this circuit causes energization of the field winding 21 to move the valve I4 towards an-open position.

Movement of the valve I4 towards an open position causes right hand movement of the slider 35 with respect to the balancing potentiometer coil 36, and due to the parallel relationship pointed out above, a circuit iscompleted from the junction of the relay coils 69 and 10 through wires I04, I01 and I08, resistance I09, wire IIO, slider 35, the right hand end of the balancing potentiometer coil 36, wires 98 and 96, and protective resistance 95 to the relay coil 69, to cause partial short-circuiting of the relay coil 69 to decrease the energization thereof and increase the energization of the relay coil 10. It 'will be remembered at this point that the energization of the relay coil 69 was increased more than the energization of the relay coil 10 by movement of the switch arm 62 irito engagement with the contact 65. When the slider 35 has moved sufficiently far to the right so as to rebalance the energizations of the coils 69 and 10, the switch arm 12 is moved out of engagement with the contact 13 to the mid position shown in the drawings, to break the circuit through the field winding 21 to stop further opening movement of the valve I 4.

Movement of the valve I4 towards an open position in this manner increases the heating fluid admitted to the heat exchanger or radiator I I in the space I0 to raise the temperature of the space. When the space temperature has been increased to '12 degrees, as illustrated, the relay coil 59 is deenergized to move the switch arm 62 out of engagement with the contact 65 and into engagement with the contact 61. Movement of the switch arm 62 into engagement with the contact 61 completes a partial shunt circuit from the junction of the coils 69 and 10 through wires I04 and I05, resistance I06, switch arm 62, contact 61, wire II2, slider 41, the right hand end of the potentiometer coil 48, wires 91 and 96, and protective resistance 95 to the relay coil 69. When the switch arm 62 is moved into engagement with the contact 61, the slider 41 is placed in control and since the resistance through the right hand endrof the potentiometer coil 48 is less than the resistance through the left hand end thereof, completion of this circuit causes partial shortcircuiting of the relay coil 69 to decrease the energization thereof and increase the energization of the coil 10. Increasing the energization of the coil 10 in this manner causes movement of the switch arm 12 into engagement with the contact 14 to complete a circuit from the secondary 90 through wires 93 and 94, a small number of turns of relay coil 10, wire II5, contact 14, switch arm 12, wire II6, field winding 28, wire II9, limit switch 33, and wires I20 and SI, back to the secondary 90. Completion of this circuit causes energization of the field winding 28 to move the valve I4 towards a closed position.

Movement of the valve I4 towards, aclosed position causes left hand movement of the slider 35 with respect to the balancing potentiometer coil 36 to complete a partial shunt circuit from the junction of relay coils 69 and 10, through wires I04, I01 and I08, resistance I09, wire IIO, slider 35, the left hand end of the balancing potentiometer coil 36, wires I03 and I00, and protective resistance 99, to the relay coil 10. Completion of I this circuit causes partial short-circuiting of the relay coil 10 to decrease the energization thereof and increase the energization of the relay coil 69, it being remembered that the relay coil 10 was energized more than the relay coil 69 by movement of the switch arm 62 into engagement with the contact 61. When the slider 35 has moved sufficiently far to the left to re-balance the energizations of the relay coils 69 and 10, the switch arm 12 is moved out of engagement with the contact 14 to the mid position shown in the drawings, which breaks the circuit through the field winding 28 to stop further closing movement of the valve I4. Movement of the valve I4 towards a closed position in this manner decreases the supply of heat to the space I0.

In this manner the valve I4 is moved towards an' open position upon a call for heat from the space thermostat I8 and is moved towards a closed position when the space thermostat I8 is satisfied, the amount of opening and closing movement being fixed by the position. of the sliders 46 and 41. Movement of the slider 46 towards the left would cause greater opening movement, and movement of the slider 41 to the right would cause greater closing movement. With the sliders 46 and 41 fixed with respect to each other, the amount of opening movement and the amount of closing movement is constant. This amount may be varied by adjusting the sliders 46 and 41 with respect to each other.

' It will be noted that the circuits through the field windings 21 and 28 of the motor I6 are completed through the limit switches 33 and 34 and through a small number of turns of the relaycoils 69 and 10. Therefore, the circuits through the field windings 21 and 28 are broken if the valve I4 should be moved. to either extreme open or closed position. Also the passing of the circuit through a small number of turns of the relay coils 69 and 10 increases the energization of these coils respectively, forcibly maintaining the switch arm 12 in engagement with the contacts 13 or 14 to prevent relay chatter.

By reason of the above described construction and mode-of operation, a predetermined amount of heat is being delivered to the space I when the space thermostat is satisfied, to maintain the space temperature at the desired value, and when the space temperature decreases so that the space thermostat I8 calls for heat a slightly larger amount of heat is delivered to the space I0 during the period of call for heat. The difference in the amounts of heat delivered to the space I0, depending upon whether the space thermostat is satisfied or calling for heat, is determined by the relative positions of the sliders 46 and 41. In order to adjust the amount of heat delivered to the space I0 in accordance with changes in the heating load, the motor I1 is utilized for operating the sliders 46 and 41 to the left or right with respect to the potentiometer coil 48. Since, as pointed out above, the per cent of total time that the space thermostat is calling for heat forms a good indication of the heating load, I utilize the motor I1, which continually operates in one direction or the other, for moving the sliders 46 and 41 to the left or right with respect to the potentiometer coil 48. Movement of the sliders 46 and 41 to the left I substantially constant at each limit.

causes partial short-circuiting of the relay coil to move the valve I4 towards an open position to supply more heat to the space I0. Likewise, movement of the sliders 46 and 41 to the right causes partial short-circuiting of the relay coil 69 to move the valve I4 towards a closed position to supply less heat to the space I0.

Upon a demand for heat by the space thermostat I8 so as to energize the relay coil 59, the switch arm 6| is moved into engagement with the contact 64 to complete a circuit from the line wire 11 through wire I22, switch arm 6|, contact 64, wire I23, limit switch 50, wire I24, field winding 40 and wire I25, back to the other line wire 16. Completion of this circuit causes energization of the field winding 40 to move the nut 44 to the left, and consequently the sliders 46 and 41 to the left. Therefore, the valve I4 is not only opened the predetermined amount, as determined by the movement of the switch arm 62 into engagement with the contact 65, but the valve I4 is movedfurther, towards an open position by the left hand movement of the slider 46. When the space temperature rises to 72 degrees to deenergize the relay coil 59, the switch arm BI is moved into engagement with the contact 66 to complete a circuit from line wire 11, through wire I22, switch arm 6|, contact 66, wire I26, limit switch 5|, wire I21, field winding 4| and wire I25, back to the line wire 16. Completion of this circuit causes energization of the field winding M to move the nut 44 to the right, and consequently to move the sliders 46 and 41 to the right. Therefore, when the space temperature is slightly above the desired value, indicating that there is no longer a demand for heat, the valve I4 is not only moved the predetermined distance towards the closed position as the result of movement of the switch arm 62 into engagement with the contact 61, but is moved further towards a closed position by the movement of the slider 41 to the right with respect to the potentiometer coil 48.

It is seen that when the space thermostat is calling for heat, the valve I4 is moved continuously towards an open position to increase the supply of heat to the space and that when the space thermostat I8 is satisfied the valve I4 is continually moved towards a closed position to supply less heat to the space I0. Since the thermostat I8 maintains the relay coil 59 energized a relatively great per cent of the total time when the heating load is great, the nut 44 is moved towards the left a greater amount than towards the right. Likewise, when the heating load is relatively small so as to maintain the relay coil 59 energized a relatively small per cent of the total time, the nut 44 is moved towards the right a greater distance than'towards the left. In this manner the nut 44 is positioned towards the left upon an increase in heating load and is positioned towards the right upon a decrease in heating load. When the heating load is increased, the valve I4 is moved farther towards an open position and when the heating load is decreased the valve I4 is moved farther towards a closed position. When substantially the correct amount of heat is being delivered to the space I0 for a given load condition movement of the nut 44 to the right will equal movement of the nut to the left, the net result being that the rate of heat delivery to the space is under these conditions the valve I4 will be open Also,

the predetermined amount the same length of time it will be closed the predetermined amount whereby equal heat increasing and heat decreasing periods will be obtained. In this manner the correct amount of heat is delivered to the space I to maintain the temperature thereof absolutely within predetermined limits, the rate of heat supply being adjusted with changes in the heating load.

The above structure and mode of operation gives satisfactory results as long as the steam pressure is maintained at a constant value. However, it is often the case that the steam pressure of a steam heating system such as disclosed in Figure l is not constant at all times. Since the amount of heat delivered to a space is dependent upon the steam pressure, it is desirable to maintain constant predetermined steam pressures in order to obtain an accurate control of the space temperature. A pressure regulator could be installed in the supply pipe I upstream of the valve I4 and satisfactory operation would be obtained. By utilizing the pressure regulator downstream of the valve I4 and generally designated at I9, constant predetermined steam pressures are not only provided but accurate calibration of the valve I4 is not required. The pressure regulator I3 may comprise a bellows I29 connected by a pipe 530 to the steam pipe I3 downstream of the valve I4. Th bellows I 29 is adapted to operate a slider I 4| with respect to a potentiometer coil I 32, the arrangement being such that as the steam pressure in the pipe I3 increases, the slider IN is moved upwardly with respect to the potentiometer coil I32 and as the steam pressure decreases, the slider I3I is moved downwardly with respect to the potentiometer coil I32. end of the potentiometer coil I32 is connected by a wire I33 to the right hand end of the potentiometer coil 48, the lower end of potentiometer coil I32 is connected by a wire I34 to the junction of wires IUI and 102, and the slider BI is connected by a wire I35 to the junction of wires MT and H38. It is, therefore, seen that the potentiometer coil I32 is connected in parallel with the secondary 9B, relay coils St and It, the balancing potentiometer coil 36 and the potentiometer coil 48. It is also seen that the slider I3I is connected to the slider 35 of the balancing potentiometer coil 36, to the junction of the relay coils 69 and "I0, and to either sliders 46 or 41 associated with the potentiometer coil 58.

omitting for the time being the operation of the sliders 46 and 41 and the potentiometer coil 48, movement of the slider I3I upwardly as av result of an increased steam pressure in the pipe I3 causes a partial short-circuiting of the relay coil 69 to decrease the energization thereof and increase the energization of the relay coil ID to move the valve 54 towards a closed position. Movement of the valve I4 towards a closed position decreases the energizatlon of the relay coil I0 and increases the energization of the relay coil 69 to rebalance the encrgizations thereof in the manner pointed out above. Therefore, the amount of closing movement of the valve I4 is proportional to the pressure increase in the pipe I3. Movement of the slider I3I downwardly as a result of a decrease in steam pressure in the pipe I3 causes partial short-circuiting of the relay coil ill to decrease the energization thereof and increase the energization of the relay coil 69 to cause movement of the valve I4 towards an open position. Move- The upper ment of the valve I4 towards an open position causes partial short-circuiting of the relay coil 69 to decrease the energization thereof and to increase the energization of the relay coil 10, and when the energizations of the relay coils 69 and Ill are rebalanced further movement of the valve I4 towards an open position is prevented. In this manner the valve I4 is positioned in accordance with the steam pressures in the pipe i3 to maintain constant predetermined pressures in the pipe I3.

When the pressure controller i9 is utilized in the system disclosed in Figure 1, the resistance I06 in series with the sliders 46 and 47 operated by the motor i7 is used to decrease the sensitivity of the potentiometer operated by the motor I I whereby the controller I9 becomes the main control and the motor I! becomes a compensating control. The operation of the motor H as a compensating control is identical with that outlined above for the main control, with the exception that the motor I! operates to adjust the effective control point of the pressure controller i9 whereby the efiective pressure setting of the pressure controller I9 is varied in accordance with changes in the heating load on the system. The resistance I09 in series with the slider 35 of the balancing potentiometer is provided to decrease the sensitivity of the balancing potentiometer whereby full range movements of the controller I3 and the motor H are required to move the valve I4 to either extreme position. By reason of the construction shown in Figure 1, utilization of the pressure controller 59 maintains constant predetermined pressure conditions in the steam pipe I3 and the values of these pressures may be adjusted in accordance with the per cent of total time that the thermostat is calling for heat, that is, the heating load on the heating system. If constant steam pressures are assured there is no need for the pressure controller I3 and, therefore, the system described above may be utilized to obtain an accurate temperature control.

Referring now to Figure 2, I have disclosed the same general heating system for maintaining the space temperature at the desired value, as in figure 1. The heating system utilizes a valve Id for controlling the supply of heating fluid, such as steam, through a pipe l3 and risers i2 to heat exchangers or radiators i 5 located in spaces to be heated Ill. The valve id of this form of my invention is operated by a proportioning motor It in the same manner outlined in the modification disclosed in Figure 1. The proportioning motor I6 is controlled by the motor IT in exactly the same. manner. Instead of utilizing a space thermostat responsive to the temperature of the space to be heated for determining the per cent of total time that there is a demand for heat, I utilize in this modification an outdoor controller generally designated at Mt, which may be of the type shown and described in application, Serial No. 512,887, filed by Daniel G. Taylor on February 2, 1931, new Patent No. 2,065,835, dated Dec. 29 1936. The outdoor controller Mil is shown to comprise a mass which may take the form of a metallic block M5 which is hollowed out to receive a container I4?! in which a bimetallic element 53 is mounted on a post M8. 'The bimetallic element 53 operates contacts 54 and 56 with respect to contacts 55 and 51 in the same manner that the bimetallic 53 of the space thermostat Id of Figure 1 operates these contacts. The container M7 is closed at the top by a cover I49 so that the bimetallic element 53 responds to the temperature of the block I in the same manner that the bimetallic element 53 of Figure 1 responds to the temperature of the space I0 of Figure 1. The block I45 is heated by a heater I46 and is cooled by the outdoor atmosphere at a rate dependent upon outdoor temperatures,

. wind velocity and solar radiation. The elements so far described, comprising the outdoor controller I40, may be suitably mounted in a housing I50 to protect the same from the elements.

The system, utilizing the outdoor controller disclosed in the above referred to Taylor application, comprises an outdoor controller responsive to outdoor atmospheric conditions, including temperature, wind velocity and solar radiation, for controlling the temperature within the building. Heating means are provided in the building for supplying heat to the building and heating means are also supplied in the outdoor controller for supplying heat to the outdoor controller. The two heatingmeans are proportioned according to the heat losses from the building and from the outdoor controller. A thermostatic device is provided for responding to the temperature within the outdoor controller and when this thermostatic device calls for heat both of the heating means are energized to deliver heat to the building and to the outside controller. Due to the proportional relationship of the heating means within the heat losses of the building and the outside controller, a definite temperature is maintained in the building and the outside controller so that by responding to the temperature of the outside controller the thermostatic device maintains a substantially constant or normal temperature within the building. Therefore, the thermostatic means in the outdoor controller responds to a demand for heat to operate the building heating means, and when the load conditions of the building are great the outdoor controlleris demanding heat a relatively great per cent of the total time, and when the heating load of the building is relatively small the outdoor controller is calling for heat only a relatively small per cent of the total time.

- The outdoor controller of the Taylor application may be utilized in my invention 'for determining the per cent of total time that there is a demand for heat, providing the heat supply to the outdoor controller is adjusted in the same manner that the heat supply to the building is adjusted, in order that the proportional relationship required for the satisfactory operation of the Taylor system may be maintained. In order to so adjust the heat supply to the outdoor controller I40, I have provided sliders I52 and I53 mounted on the insulating abutment member 49, and the sliders I52 and I53 are adjustably mounted as are the sliders 46 and 41. Sliders I52 and I53 are adapted to slide across a resistance I54. The sliders I52 and I53 are connected by wires I55 and I56 to contacts I51 and I58, which are adapted to be engaged by a switch-arm I59, the switch arm I59 being operated by the relay coil 59. Upon energization of the relay coil 59, the switch arm I59 is moved into engagement with the contact I5! and upon deenergization thereof the switch arm I59 is moved into engagement with the contact I58. The resistance I54 is connected by a wire I60 to one end of the heater I46 located in the outdoor controller I40. The other end of the heater I46 switch arm I59 is connected by a wire I64 to the other line wire 'II. When the switch arm I59 is moved into engagement with the contact I5'I, the slider I52 is placed in control, and when the switch arm I 59 is moved into engagement with the contact I58, the slider I53 is placed in control.

Upon a call for heat by the outdoor controller I40 so as to energize the relay coil 59, the switch arm 62 is moved into engagement with the contact 65 to increase the supply of heat to the spaces I0 in the manner pointed out with respect to Figure 1, and the switch arm I59 is moved into engagement with the contact I5'I to complete a circuit from line wire 'I'I through wire I64, switch arm I59, contact I5'I, wire I55, slider I52, resistance I54, wire I60, heating element I46, wire ISI? variable resistance I62 and wire I63, back to the other line wire I6. Completion of this circuit causes energization of the heater I46 to raise the temperature of the block I45. 20

When the temperature of the block I45 has risen to such a value as to deenergize the relay coil 59, the switch arm 62 is moved into engagement with the contact 61 to supply a reduced amount of heat to the space in the manner pointed out with respect to Figure 1, and the switch arm I59 is moved into engagement With the contact I58 to complete a circuit from the line wire 'II through wire I 64, switch arm I59, contact I58, wire I56, slider I53, resistance I54, wire I60, heater I46, wire I6I, variable resistance I62, and wire I63,back to the other line wire I6. The heater I46 is maintained energized by this circuit but at a lesser rate by. reason of the increase in resistance afforded by placing the slider I53 in control instead of the slider I52. 'Therefore, upon a call for heat by the. outdoor controller, the heating element I46 is energized at a relatively high rate, and when the outdoor controller is satisfied the heater is energized at a relatively lower rate. The difierence in rate at which the heater is energized is dependent upon the relative positions of the sliders I52 and I53. By adjusting the sliders I 52 and I 53 with respect to the sliders 46 and 41, the relative amounts of heat delivered to the outdoor controller I40 and to the spaces I0 may be adjusted to maintain theproportional relationship outlined above for the satisfactory operation of the control system.

Upon a call for heat by the outdoor controller, the switch arm 6| is moved into engagement with the contact 64 to operate the motor IT, to increase the heat supply to the spaces I0 in the manner pointed out with respect to Figure 1,

and also increases the supply of heat to the outdoor controller I46 by the left hand movement of the slider I52. Likewise, when the outdoor controller I40 is satisfied, the switch arm 6| engages the contact 66 to operate the motor I! to decrease the supply of heat to the spaces I0 in the manner pointed out with respect to Figure 1, and also decreases the supply of heat to the outdoor controller I40 by reason of the right hand movement of the slider I53. The heat input to the outdoor controller I40 is controlled in exactly-the same manner as the heat input to the building, therefore, establishing and maintaining the proportional relationship which permits the control of the building heating means by the outdoor controller I40. Both means for supplying heat to the spaces I0 and to the outdoor controller I40 are controlled in accordance to the per cent of total time that there is a demand for heat and consequently the spaces dii I!) are maintained at the desired temperature regardless of changes in the heating load as caused by changes in outdoor temperature, wind velocity and solar radiation. Like reference characters have been used throughout Figures 1 and 2 where like elements are used. As in the preceding modification, the nut 44 will be moved an equal amount in both directions when the correct amount of heat is being delivered to the building,

whereby equal heat increasing and decreasing periods are obtained.

It has been found that even with a substantially constant source of steam pressure, the rate of flow of steam through the control valve I! may not be constant and may vary. These variations in rate of flow may be attributed to'changes in steam supply pressures, to changes in rate of condensation in the heating system which results in varying outlet pressures at the valve, to the condition of the heating system just as the valve is opened to a greater extent depending upon whether the system is full or only partially full of steam, to the frequency of operation of the valve, to the length of time in which the valve is maintained in a valve opening position, and to other causes. Therefore, a valve which controls the supply of steam to a heating system does not necessarily admit twice as much steam when the valve is moved to a given position, say twenty minutes, than when the valve is moved to the same position for only ten minutes. It is, therefore, desirable, when an extremely accurate temperature control is needed, to utilize a flow regulator generally designated at Ml, for maintaining predetermined constant rates of flow of steam to the heat exchangers in the spaces It, and to adjust these rates of flow of heating fluid to the heat exchangers in accordance with the heating load on the heating system. For this purpose, I have provided a how regulator generally designated at Mt, which may comprise an orifice H2 in the pipe 83, the downstream side of the orifice i'l2 being connected by a pipe M3 to the upper portion of an enclosed chamber lid, and the upstream side of the orifice H2 being connected by a pipe M5 to the lower portion of the enclosed chamber tilt. Located in the enclosed chamber HE is an inverted hell H3 which is sealed by liquid, therefore, forming two pressure chambers, one above the hell HS and the other below or in the bell. The bell H6 is connected by a rod ill to the slider act, which may be pivoted on a bracket Wt. Flow regulators of this type are old in the art and a specific description thereof is not considered necessary, it being sufficient to state that as the flow of heating medium through the pipe is increases, the slider lti is moved upwardly with respect to the potentiometer coil l3? and as the flow of heating medium decreases, the slider SM is moved downwardly. The slider 536 and the potentiometer coil 532 are connected into the control system in the same manner as the slider i3iand the potentiometer coil I32 of the pressure regulator it of Figure 1 are connected into the control system. Therefore, in this modification the flow regulator l 'H operates to maintain predetermined rates of flow of heating medium in the pipe l3 and these rates of flow of heatin medium are adjusted in accordance with the demand for heat, to maintain the space temperature at the desired value regardless of changes in the heating load.

Therefore, in this modification I have provided a temperature control system wherein the space temperature is maintained at a desired value regardless of changes in the heating load and wherein the heating system is adjusted in accordance with the per cent of time during which there is a call for heat. I utilize the outdoor controller in this modification for determining the .per cent of total time that there is a demand for heat, since in large buildings it is often difficult to find or locate a suitable place for a control thermostat which will indicate the average temperature condition of the building. Therefore, in large buildings of this type it may be preferable to use the outdoor controller Ml] for controlling the heating system in the manner indicated in Figure 2, but where an average loca- 'tion may be found in an ordinary size building the space thermostat it of Figure 1 may be utilized. I have also provided in this modification a means responsive to the condition of the heating medium (rate of flow of the heating medium) for maintaining the condition of the heating medium at desired values and adjusting these values in accordance wtih the per cent of time that there is a demand forheat in order to maintain the space temperature at the desired value regardless of changes in the heating load.

Referring now to Figure 3, I have disclosed a modified form of my invention for controlling original heating equipment that is intermittently operated, as distinguished from proportioning equpment, as disclosed in Figures 1 and 2. The means responding to the per cent of total time that there is a demand for heat is the same as that of Figure 1 and may comprise the space thermostat it for controlling the operation of the motor il in exactly the same manner as in Figure '1. Like reference characters have been used for designating the elements of the space thermostat it, the motor ill, and the connec= tions therebetween.

I have shown this form of my invention applied to a hot air furnace ltd having a bonnet iti and fired by an oil burner i182. Located in the bonnet itfl is a temperature responsive device generally designated at I832. The temperature responsive device H33 responds to the bonnet temperature of the hot air furnace itd, and may comprise a sleeve iii i rotatably mounted in the bonnet and to which is secured amend or a bimetallic helix M35. The other end of the pimetallic helix is connected to a torquerod itt which extends through the sleeve i 8% and has secured on the outer end thereof a bracket M7. The bracket it? carries mercury switches M38 and 589, the mercury switch its performing a high limit function and the mercury switch 5-89 performing a low limit function. The arrangement is such that upon an increase in bonnet temperature, the bracket 8 87 is rotated in a clockwise direction, and upon decrease in bonnet temperature, the bracket it?! is rotated in a counterclockwise direction. The mercury switches #88 and ltd are so positioned with respect to each other that upon a decrease in temperature to a predetermined value the mercury switch m9 is moved to a circuit making pdsition and upon an increase in temperature a predetermined amount above said predetermined value the mercury switch 188 is moved to a circuit breaking position, and this difference in temperatures may be illustrated as 29 degrees.

The sleeve W8 is rotatably adjusted by a lever i939 which is connected by a pitman it! to a bracket E82 suitably secured to the nut it operated by the motor ii. The not H also carries an abutment I93 which is adapted to engage the limit switches 58 and 5I at either extreme posi-. tion of the nut 88. When the nut 88 is moved towards the right, the sleeve I88 is rotated in a clockwise direction to lower; the temperature setting of the thermostat I83, and when the nut 88 is moved to the left, the sleeve I88 is rotated' in a counter-clockwise direction to raise the setting of thethermostat I83.

Relay coil 59 in addition to controlling the switch arm 8| with respect to contacts 69 and 68 for controlling the operation of the motor II, also operates a switch arm I95 with respect to a contact I 96, the arrangement being such that when the relay coil 59 is energized the switch arm I95 is moved into engagement with the contact I98. The contact I98 is connected by a wire I9I to the line wire I I and the switch arm I 95 is connected by a wire I98 to one of the electrodes of the high limit mercury switch I88. The other electrode of the mercury switch I88 is connected by wires I99 and 208 to the oil burner I82, which in turn is connected by a wire I to the other line wire I6. One of the electrodes of the low limit mercury switch I89 is connected by a wire 288 to the junction of wires I99 and 288, and the other electrode thereof is connected by a wire 203 to the line wire 'I'I.

With the parts in the position shown in Figure' 3, the bonnet temperature is assumed to be at such a value as to supply substantially the correct amount of heat to the space to maintain the space temperature at the desired value. As the bonnet temperature decreases, the mercury switch I89 is tilted to a circuit making position to complete a circuit from line wire 'I'I through wire 283, low limit mercury switch I 89, wires 204 and 280, oil burner I82 and wire 28I, back to the other line wire I6. Completion of this circuit causes operation of the oil burner to restore the bonnet temperature to the desired value. When the bonnet temperature has been restored to the desired value, the low limit mercury switch I 89 is moved to a circuit breakingpositlon to stop operation of the oilburner I82: In this manner the oil burner I82 is intermittently operated to maintain the bonnet temperature at the value determined by the setting of the switch I 88, which value supplies an amount of heat to the space slightly less than that required to maintain the space temperature at the desired value.

When the space temperature decreases to 70 degrees, as illustrated in Figure 1, the relay coil 59 is energized to move the switch arm I95 into engagement with the contact I96 to complete a circuit from the line wire I! through wire I9I, contact I96, switch arm I95, wire I98, high limit mercury switch I88, wires I99 and 208, oil burner I82, and wire 21, back to the other line wire I6. Completion of this circuit causes energization of the oil burner I82 to raise the temperature of the heating medium in the bonnet I8I to supply additional heat to the space to restore the space temperature to the desired value, and when the bonnet temperature has been increased the twenty degrees, as illustrated, the mercury switch I88 is moved to a circuit breaking position to stop operation of the oil burner I82. When the bonnet temperature decreases as a result of stopping operation of the oil burner I82 to such a value as to move the high limit mercury switch I88 to a circuit making position the oil burner will be reenergized, providing the space thermostat is still calling for heat. Therefore, when the space thermostat is satisfied, the bonnet temperature is maintained at a predetermined temperature value, and when the space themostat is calling for heat, the bonnet temperature is maintained at a predetermined higher temperature value, the diiference in these temperature values being illustrated as 20 degrees.

Also In this modification, as in the previous modifications, when the space thermostat I8 is calling for heat, the switch arm BI is moved into engagement with the contact 88 to cause left hand movement of the nut 88 to gradually raise the temperature setting of the thermostat I83, and when the space thermostat I8 is satisfied the switch arm BI is moved into engagement with the contact 88 to move the nut 88 to the right to lower gradually the temperature setting of the bonnet thermosat I88. Since the per cent of total time that the thermostat is calling for heat varies in accordance with the heating load on the system, and since the nut 88 is moved towards the right upon a call for heat and towards the left when the space thermostat is satisfied, the nut 84 is positioned towards the rightas the heating load increases and towards the left as the heating load decreases, in the same manner as pointed out with respect to Figures 1 and 2. Therefore, as the heating load increases the setting of the furnace thermostat I83 is raised and as the heating load decreases the setting of the thermostat I83 is lowered. In this manner a condition of equilibrium is established wherein the left hand movement of the nut 88 equals the right hand movement whereby the space temperature is maintained at the desired value in accordance with changes in the heating load. "overshooting" and "undershooting of the space temperature is thereby prevented.

Although in this modification, I have shown my invention as applied to a hot airiurnace, the invention may equally as well be applied to a hot water system wherein the controller I83 could respond to the temperature of the hot water, or may also be used in connection with a steam or vapor system, and under such circumstances, the controller I83 would be responsive to steam or vapor pressures. In all instances the general mode of operation would be identical. Although I have disclosed in this modification an oil burner for the purpose of heating the space, other means may be provided, such as gas burner means,

coal stoker means, or draft damper means, which require intermittent on and oil operation.

Referring now to Figure 4, I have disclosed a control system which may operate the control systems of Figuresv 1 or 3 in response to the per cent of time which the space temperature is calling for heat as determined by the per cent ,of time which the average temperature of a building is below the desired value. In other words, Figure 4 discloses an average temperature control system for controlling the systems of Figures 1 and 3. a

A plurality of spaces of a building to be heated are generally designated at. 2H! and these spaces are each provided with radiators or heat exchangers 2I I .which receive a supply of heating fluid through pipes 2I3. The heating. fluid may take the form of either steam or hot water. The supply of steam or hot water to-each radiator 2 may be proportioned by suitable orifices-2H in a manner known in the art. Expended heating fluid is taken from radiator 2 through a pipe 2I5, and in case steam is used as the heating fluid, suitable steam traps 2I8 may be provided.

Steam orv hot'water may be delivered to vthe radiators 2 through the pipe 2I3 under the control of the valve I4 and the proportioning motor I6, as illustratedin Figure 1, or steam or hot water may be supplied to the radiators 2 from a boiler fired by an oil burner I82, as disclosed in Figure 3.; Heating fluid in the form of hot airmay be delivered tothe spaces from the hot air-. furnace of Figure3 if desired.

,Each space 2I8'may, be provided with a thermostaticcontrol. device generally designated at 2I8; which devices control a balanced relay generally. designated at, 2I9.- The balanced relay designated at 220, which in turn controls the control motor I1 and proportioning motor I6 of Figurel, or which may control the control motor I1 and the oil burner I82 of Figure 3. The arrangement is such that when the average temperature within the building falls below a predetermined value, the heat supply to the spaces 2I0 is increased and when the average temperature of the building rises above that predetermined value, the supply of heat to the building is decreased. As shown in Figure 4, the relay 220 operates the switch arm 6i with respect to contacts 64 and 66 to control the control motor I1 in the same manner as shown in Figures 1 and 3. The relay 220 also operates the switch arm 62 with respect to contacts 65 and,,61 to place the control of the proportioning motor I6 of Figure 1 under the control of either slider'46 or 41 in the manner pointed out with respect to Figure 1. If the control system of Figure 3 is to be utilized, the relay 220 may operate the switch arm I95 with respect to contact I96 of Figure 3 to control the oil burner I82 in the manner pointed out with respect to Figure 3.

The temperature controller 2H3 of the upper space 2I0 is shown to comprise a thermostatic bellows 222for operating sliders 223 and 224 with respect to resistance coils 225 and 226. The temperature controller 2I8 of the middle space 2I0 is shown to comprise a thermostatic bellows 221 for operating sliders 228 and 229 with respect to resistances 230 and 23L The temperature controller 2| 8 of the lower space '2I0 is shown to comprise a thermostatic bellows 232 for operating sliders 233 and 234 with respect to resistances 235 and 236. The arrangement of all of the temperature controllers 2! is such that when the temperatures of the spaces 2I0 increase the sliders are moved to the left with respect to their associated resistances and When temperature decreases the sliders are moved to the right with respect to their associated resistances.

The balanced relay H9 is shown to comprise a pivoted armature 238 carrying a switch arm 239 which cooperates with spaced contacts 248 and MI. The armature 238 is controlled by relay coils 242 and 243, the arrangement being such that when the coil 242 is energized more than the coil 243 the switch arm 239 is moved into engagement with the contact 240 and when the relay c il 243 is energized more than the coil 242 the switch arm 239 is moved into engagement with, the contact 24I.

A step-down transformer is generally designated at 245, the primary 246 of which is connected to some source of power, not shown. One end of the secondary 241 of the step-down transformer 245 is connected by wires 248,249 and 250 to one end of the relay coil 242. The other end of the secondary 241 is connected by wires sliders are connected by wires 26Il-and26l to sliders 223 and. 224. .The resistances-225-and- I 226 associated with these sliders 223 and 2-24 are connected by wires ,262,and 263;and protective resistances 264 and 265, to the first mentionedends of the relay coils 242 and 243.

From these wiring connections, it is seen that, the relay coils 242 and 243are series connected across the secondary 241 and that the left'hand resistances of the temperature controllers 218 are connected in series within one another and are connected in parallel with the relay coil 242, and that the right hand resistances of the temperature controllers 2I8 are connected in series with one another and are connected in parallel with'the relay coil 243. By reason of these connections, movement of the sliders of the temperature controllers M8 to the left decreases the energization of the relay coil 242 and increases the energization of the relay coil 243. Movement of the sliders of the temperature controllers 2 I8 toward the right decreases the energization of the relay coil 243 and increases the energization of the relay coil 242. With the parts in the position shown, the relay coils 242 and 243 are equally energized as the result of a desired average temperature being present in the building. In. case any temperature controller 218 should move its sliders to the right in response to a decrease in temperature affecting the same, the relay coil 242 will become more highly energized than the relay coil 243 to move the switch arm 239 into engagement with the contact 240. In case any of the temperature controllers 2I8 should move its sliders to the left in response to an increase in temperature afiecting the same, the relay coil 243 will become more highly energized than the relay coil 242 to move the switch arm 239 into engagement with the contact 24 I. From the above it is seen that when the average temperature of the building is at the desired value, the switch arm 239 is maintained midway between the contacts 248 and 2, as shown in the drawing, that if the average temperature should increase above the desired value the switch arm 239 is moved into engagement with the contact 24I and that if the average temperature of the building should decrease below the desired value the switch arm 239 is moved into engagement with the contact 240.

The relay 220 may comprise an energizing coil 218 and a bucking coil 2H for operating an armature 212 which operates a maintaining switch arm 213 with respect to a contact 214. The armature 212 may also operate the switch arms BI and 62 of Figure 1, or the switch arms 6| and I95 of Figure 3. The arrangement is such that when the energizing coil 218 is energizedth'es'witch arms are moved to the left from the position shown inthe drawing, and that when both the energizing coil 210 and the bucking coil 21I are energized or when neither coil 21!) or 21! are energized, the switch arms are moved'to the right to the position shown in the drawing by means of springs, gravity or other means, not

, shown.

Movement of the switch arm 239 of the halanced relay 2I9 into engagement with the contact 240 as a resultof a decrease in the average temperature of the building, completes a circuit from thefright hand end of'the secondary 241 through wires 25I, 216 and 211, energizing coil 210, wire 216, switch arm 239, contact 246 and wires 219, 249 and 248 back to the other end of the secondary 241. Completion of this circuit causes energization of the energizing c'oil 210 to move the switch arms 213, 6|, 62 and I into engagement with their respective contacts 214, 64, 65 and I96. Movement of the switch arm 213 into engagement with the contact 214 completes a maintaining circuit for the energizing coil 210 from the right hand end of the secondary 241 through wires 25I, 216 and 211, energizing coil 210, wire 286, cotnact 214, switch arm 213 and wires 28I and 248 back to the other end of the secondard 241. Completion of this maintaining circuit maintains the energizing coil 210 energized until such time as the switch arm 239 shall move into positive engagement with the contact 24I. Movement of the switch arm 6I into engagement with the contact 64 as a result of energization of the energizing coil 210 causes gradual increasing of the pressure or rate of fiow of the heating fluid in the manner described with respect to Figures 1 and 3. Movement of the switch arm 62 into engagement with the contact 65 as a result of energization of the energizing coil 210 increases immediately a predetermined amount the pressure or rate of flow of heating fiuid in the manner pointed out with respect to Figure 1. Movement of the switch arm I95 into engagement with the contact I96 causes immediate operation of the oil burner I82 in the manner pointed out with respect to Figure 3. It follows then that movement of the switch arm.239 into engagement with contact 240 in response to a decrease in the average temperature causes the supply of additional heat to the spaces 2 III in the building to restore the average temperature of the building to normal.

When the average temperature of the building rises slightly above normal, the switch arm 239 is moved into engagement with the contact 2 to complete a circuit from the right hand end of the secondary 241 through wires 25I and 216, bucking coil 21I, wire 282, contact 24I, switch arm 239, wires 218 and 290, contact 214, switch arm 213 and wires 28I and 248 back to the other end of the secondary 241. Completion of this circuit causes energization of the buckin coil 21I which counteracts the action of the energizing coil 210, whereby the switch arms 213, 6I, 62 and I95 are moved to the right to the positions shown in the drawings. Movement of the switch arm 213 out of engagement with the contact 214 in this manner breaks the circuit through the bucking coil 21I and also the maintaining circuit through the energizing coil 210, whereby both coils 210 and 2H are cfieenergized and the switch arms remain in the position shown in the drawing. Movement of the switch arm 6I into engagement with the contact 66 operates motor I1 of Figures 1 and 3 in such a-direction as to gradually decrease the supply of heat to the spaces. Movement of the switch arm- 62 into engagement with contact 61 immediately decreases at predetermined amount the supply of heat to the spaces if the control system of Figure 1 is used. Movement of the switch arm I95 out of engagement with the contact I96 returns the control of the oil burner I92 to the low limit setting it the control system of Figure 3 is used. It follows then that when the average temperature in the building rises above a predetermined value, the supply of heat to the building is decreased a predetermined amount and the supply of heat is further gradually decreased as long as the average temperature remains above normal.

From the above it is seen that in this modification shown by Figure 4 I have not only provided a meanswhereby heat is supplied to a building in accordance with the per cent of total time that there is a demand for heat to supply just the correct amount of heat to maintain the building temperature constant, but I have made my control system responsive to the average temperature of the building and not to the temperature of a particular portion of the building. This type of control system like that of Figure 2 may be used where it is impossible to find a location in a building the temperature of which represents the average temperature of the building.

It is to be understood that the specific temperature values used in the description of my invention are for purposes of illustration only, and that other temperature values may be selected as desired. It is also to be understood that my control systemmay be advantageously applied to refrigerating systems for summer cooling, and would require only reversal of the thermostat control devices. Although I have disclosed various forms of my invention, other forms thereof may become obvious to those skilled in the art, and consequently my invention is to be limited only by the scope of the appended claims and prior art.

I claim as my invention:

1. In a temperature control system, the combination of means for supplying heatto a space, valve means in control of the supply of heat, thermostatic means responsive to'space temperatures for controlling said valve means to increase the supply of heat to the space upon a call for heat and to decrease the supply of heat when the thermostatic means is satisfied, the increase and decrease being substantially constant, and means controlled by said thermostatic means for additionally increasing or decreasing the supply of heat in accordance with the per cent of time that the space thermostat is calling for heat or is satisfied.

2. In a temperature control system, the combination of heating means for abuilding, a controller outside of the building and subject to the same ambient conditions as the building and including heating means and thermostatic means, the thermostatic means controlling both heating means to increase the supply of heat to the building and the controller upon acall for heat and to decrease the supply of heat when the thermostatic means is satisfied,- and-means controlled by said thermostatic means for additionally increasing and decreasing the supply of heat to the building heating means and the controller heating means in response to the per cent of time that the thermostatic means is calling for heat or is satisfied.

3. In a temperature control system, the combination of electrically operated means for controlling a condition of a temperature changing medium for regulating the temperature in a space, means responsive to a value of said condition, a pair of switching mechanisms operated by said last named means in response to changes in the value of said condition, a space thermostat responding to changes in space temperature, one

of said switching mechanisms and said space thermostat controlling said electrically operated means upon a call for a temperature change by said space thermostat, the other ofsaid switching mechanisms being operative to control said electrically operated means when said space thermostat is satisfied and the value of said condition attains a predetermined value, and means controlled by said space thermostat for adjusting said condition responsive means whereby the settings of both switching mechanisms are adjusted.

4. In a temperature control system, the combination of electrically operated means for controlling a condition of a temperature changing medium for regulating the temperature in a space, means responsive to a value of said condition, a pair of switching mechanisms operated by said last named means in response to changes in the value of said condition, a space thermostat responding to changes in space temperature, one of said switching mechanisms and said space thermostat controlling said electrically operated means upon a call for a temperature change by said space thermostat, the other of said switching mechanisms being operative to control said electrically operated means when said space thermostat is satisfied and the value of said, condition attains a predetermined value, and means continuously operable in opposite directions to raise or lower the setting of said condition responsive means, said continually operable means being controlled by said space thermostat.

5. In a temperature control system the combination of heating means for a space, means for regulating the temperature of said heating means, a space thermostat for operating said regulating -means to increase the temperature of said heating means a predetermined amount upon a demand for heat, and for decreasing the temperature of said heating means said predetermined amount upon said' space thermostat becoming satisfied, and means also controlled by said space thermostat for adjusting said regulating means to further increase or decrease the temperature of said heating means in accordance with the proportion of time during which the space thermostat is calling for heat or is satisfied.

6. In a temperature control system, the combination of heating means for a space, means for regulating the temperature of said heating means, a space thermostat for operating said regulating means to increasethe temperature of said heating means a predetermined amount upon a demand for heat, and for decreasing the temperature of said heating means said predetermined amount upon said space thermostat becoming satisfied, and means continuously operated in one direction or the other dependent upon whether the space thermostat is calling for heat or is satisfied for adjusting the controlling means to further increase or decrease the condition of the heating means.

7. In a system for controlling the temperature of a space, a temperature changing medium, means foreirculating said temperature changing medium to the space whose temperature is to be controlled, a space thermostat, and means for regulating the temperature changing effect of said medium, said space thermostat upon a demand for a change in temperature causingsaid last mentioned means to increase the temperature changing effect of said medium a predetermined amount and thereafter continuously increase said efiect, said space thermostat upon satisfaction causing said regulating means to decrease said effect a predetermined amount and thereafter continuously decrease said effect.

8. In a heating systemfor controlling the temperature of a space, a heating means for heating a medium, adapted tolinfluence the space temperature, a control device responsive to the temperature of said heatingmediumfor controlling said heating means to maintain the temperature of said heating medium at a certain value, power means for continuously, adjusting said control device to steadily increase or decrease said temperature value, and a thermostat responsive to space temperature, said thermostat on an increase in space temperature to a predetermined high value reversing said power means to steadily decrease the temperature of said heating medium, and on a decrease in space temperature to a predetermined lower value again reversingsaid power means to steadily increase the temperature of said heating medium until the space temperature again reaches said predetermined high value, whereby the average space temperature maintained will be half way between the high and low limits regardless of the load on the heating system'.

9. In a heating system for controlling the temperature of a space, a heating device for heating the medium adapted to deliver heat to said space,

an electrical fuel burner for delivering heat to said heating device, switching means in control of said fuel burner, thermalmeans responsive to the temperature of said heating medium actuating said switching means to energize and deenergize said fuel burner to control the temperasaid heating medium when the space temperature reaches a predetermined high value, whereby the average space temperature maintained will be approximately. half way between said high and low values.

10. In a system for controlling a condition, the

combination of condition changing means for changing the condition to be controlled, adjustable control means responsive to a condition directly associated with the condition changing means to control the condition changing eiiect of the condition changing means in accordance with the adjustment of the adjustable control means, means continuously operating in one direction or the other for continuously and gradually ad'- justing the adjustable control means to increase or decrease the condition changing effect of the condition changing means, and second control means indicative of the value of the condition to be controlled for increasing or decreasing a predetermined amount the condition changing eflect of the condition changing means and for controlling the direction of operation of the continu i ously operating means.

ll. In a temperature control system for con-.

trolling the temperature of a space, the combination of temperature changing means for changing the temperature of the space, adjustable control means, means responsive to a condition directly associated with the temperature changing means to control the temperature changing eflect of the temperature changing means in accordance with the adjustment of the adjustable control means, means continuously operating in'one direction or the other for continuously andgradually adjusting the adjustable control means to increase and decrease the temperature changing eflect of the temperature changing means, and second control means indicative of the value of the space temperature for increasing or decreasing a predetermined amount the temperature changing effect of the temperature changin means and for controlling the direction of operation of the continuously operating means.

12. In a system for controlling a condition, the combination of a condition changing means for controlling the condition to be controlled, means including control means responsive to a condition directly associated with the condition changing means and control means indicative of the value of the condition to be controlled acting conjointly for increasing a predetermined amount the condition changing effect of the condition changing means upon a demand for an increased condition changing effect, for additionally and gradually increasing the condition changing effect as long as the demand continues,

for initially decreasing a predetermined amount the condition changing effect of the condition changing means when the demand becomes satisfied and for additionally and gradually decreasing the condition changing eflect of the condition changing means as long as the demand is satisfied.

13. In a temperature controlsystem for controlling the temperature of a space, the combination of temperature changing means for changing the temperature of the space, means including. control means responsive to a condition directly associated with .the temperature changing means and control means indicative of the value of the space temperature acting conjointly for initially increasing a predetermined amount the temperature changing efiect of the temperature changing means upon a demand for an increased temperature changing efiect, for additionally and gradually increasing the temperature changing effect as long as the demand continues, for decreasing a predetermined amount the temperature changing efiect of the temperature changing means when the demand becomes satisfied and for additionally and'gradually decreasing the temperature changing efiect of the temperature changing means as long as the demand is satisfied.

14. In a temperature control system for a space, the combination of heating means for the space, electrically operated means controlling the heating efiect of the heating means, a pair of current controlling mechanisms for controlling the electrically operated means, thermostatic means indicative of the value of the space temperature operative upon a demand for heat to place one of the current controlling mechanisms in control of the electrically operated means to increase a given amount the heating effect of the heating means and operative when the demand for heat is satisfied to place the other current controlling mechanism in control of the electrically operated means to decrease a given amount the heating efiect of the heating means, and means controlled bythe thermostatic means to increase additionally and gradually the heating effect of the heating means long as the thermostatic means is demanding heat and to decrease additionally and gradually the heating efiect of the heating means as long as the demand for heat by the thermostatic means is satisfied.

15. In a temperature control system for a space, the combination of heating means for the space, electrically operated means controlling the heating effect of the heating means, a pair of current controlling mechanisms for controlling the electrically operated means, thermostatic means indicative of the value of the space temperature operative upon a demand for heat to place one of the current controlling mechanisms in control of the electrically operated means to increase a given amount the heating efiect of the heating means and operative when the demand for heat is satisfied to place the other current controlling mechanism in control of the electrically operated means to decrease a given amount the heating efiect of the heating means, and means controlled by the thermostatic means for adjusting the current controlling mechanisms to increase additionally and gradually the heating effect of the heating means as long as the thermostatic means is demanding heat and to decrease additionally and gradually the heating effect of the heating means as long as the demand for heat by the thermostatic means is satisfied.

16. In a temperature control system, the combination of electrically controlled temperature changing means for changing the temperature of a heat exchange medium, temperature responsive means responsive to the temperature of said heat exchange medium, a pair of switching mechanisms operated by said temperature responsive means in response to changes in the temperature of said heat exchange medium, a space thermostat responsive to changes in temperature of a space whose temperature is being controlled by said heat exchange medium, one

of said switching mechanisms and said space thermostat controlling the temperature changing means upon a call for a temperature change by said space thermostat, the other of said switching mechanisms controlling the temperature changing means when the space thermostat is satisfied, and means controlled by the space thermostat for adjusting said temperature responsive means whereby the settings of both switching mechanisms are adjusted.

17. In a heating system, the combination of heating means for raising the temperature of a heating medium to be supplied to a space, temperature responsive means responsive to the temperature of the heating medium, a low limit control means and a high limit control means for the heating means operated by said temperature responsive means, a space thermostat responding to changes in space temperature, means responsive to a call for heat by the space thermostat for placing the heating means under the control of the high limit control, means responsive to the space thermostat becoming satisfied for placing the heating means solely under the control of the low limit thermostat, and nieans controlled bynsaid space thermostat for continuously raising the setting of the high limit control upon a call for heat and for continuously lowering the setting of the low limit control when the space thermostat is satisfied.

WILLIAM L. McGRA'I'H. 

